1. Field of the Invention
The present invention generally relates to drill pipe tongs used in making up or breaking apart drill pipe joints and includes hydraulically or pneumatically powered upper and lower tongs which are swivelly connected for a scissoring action. Each of the tongs includes a door that is hingedly mounted at one edge and provided with a latch at the other edge to enable the doors to be swung to a completely open position for removal of the tongs from the drill pipe when desired.
2. Description of the Prior Art
Various types of tongs have been employed when making up or breaking out drill pipe joints, drill collars and the like in oil well drilling operations in which upper and lower tongs sequentially grip and release upper and lower drill pipe joints with the upper and lower tongs being moved in a swivelling or scissoring manner to thread or unthread the threaded connection between the drill pipe joints. Power operated tongs have been provided for this purpose and the following U.S. patents disclose some of the developments that have occurred in this field of endeavor:
U.s. pat. No. 2,668,689 PA1 U.s. pat. No. 2,737,839 PA1 U.s. pat. No. 2,760,392 PA1 U.s. pat. No. 2,871,743 PA1 U.s. pat. No. 3,021,739 PA1 U.s. pat. No. 3,316,783 PA1 U.s. pat. No. 3,629,927 PA1 U.s. pat. No. 3,799,009
In addition to the above-listed patents, a hydraulically actuated drill pipe tong is being manufactured in which an upper and lower tong are swivelled with respect to each other by a torqueing cylinder which can be extended or retracted to break out or make up the drill pipe as may be required. The pipe biting or gripping system utilizes a centrally-positioned single hydraulic ram which extends to move one of two opposed tong die heads into gripping or biting engagement with the pipe so as to grip the pipe for making up or breaking the joint. This tong includes a pivotally mounted latching door which can be released and pivoted to an open condition so that the tongs can be removed from the pipe. Since the opening or space provided by the gripping system of this prior tong through which the drill pipe passes when operating on pipe stands is not sufficient to permit tool joints, protectors and the like to pass, it is necessary to continuously open the latching door. This opening of the door and subsequent closing and latching of the door is a relatively time-consuming operation when running stands of drill pipe. In other words, the limited movement of the tong die head between its biting or gripping position and its released position is of such small dimension that the pipe, protectors thereon and the like are precluded from passing through the tongs unless the door is opened.